So the issue of giving the District of Columbia a vote in Congress has arisen again. On the one hand, the Constitution is quite clear in limiting congressional voting rights to "the States." Although D.C. is like a state for numerous purposes, it is not a state, and statehood is neither realistic nor desirable. And without statehood, there can be no vote.

On the other hand, I see no particular normative reason why this should be case, just historical and political reasons.

Historically, the District, like the other Territories, had too little population to be deemed worthy of Congressional representation. When a Territory had sufficient population and organization for self-government, they would apply for and receive statehood. D.C. is unique in that it has substantial population and interest in representation in Congress but no potential for statehood.

Puerto Rico is the only US territory with a larger population than DC. Their internal politics have tended to favor maintaining the status quo over statehood or independence. Since PR doesn't pay federal taxes, and the federal government has a mostly hands-off policy, their representation in Congress is a moot point. Likewise the other four territories (US Virgin Islands, Guam, Northern Marianas, American Samoa) which have the added anti-representation count of too little population to matter.

Politically, of course, any grant of representation in Congress to D.C. would inevitably be a permanent Democratic seat, much like D.C.'s three electoral votes. (By the way, the fact that the 23rd Amendment was able to pass in the '60s stuns me - was the New Deal coalition really that strong?) And that's the same barrier to any other sort of structural change to fix the severe administrative problems with our current government (unequal representation in the Senate, gerrymandering in the House and state legislatures, the confused allocation of state and federal powers that creates redundant bureaucracy and a massive disconnect between policy and implementation, etc.) - the vested interests in maintaining the current system hold the power to block any substantive reduction in their own powers.

Myself, I'd say that a constitutional amendment akin to Section 122 of the Australian Constitution, under which the Australian Capital Territory and the Northern Territory are represented in federal Parliament despite their non-statehood. But since that would realistically amount to representation for DC and DC only, such an amendment would almost certainly fail. Such are the flaws in American politics.